Divisi
Leaf spot
· Fungal
Photo: MerielGJones · CC BY-SA 4.0
Leaf spot is a group of fungal diseases that pepper the leaves of many crops — groundnut, maize, tomato and banana — with distinct dead spots. The fungus survives on old infected leaves and crop trash, and its spores are splashed up onto healthy leaves by rain and carried on the wind. In warm, wet, humid weather the spots multiply and join up, killing the leaf, so the plant sheds its lower leaves early and cannot fill its grain, pods or fruit.
Plant pests and diseases · CC0 
Scot Nelson · CC0
Why it matters
Leaf spot steals the plant's food factory — its leaves. In a bad, wet season it can cost you up to half your crop (50%) because the plant drops its leaves early and never fills its pods, grain or fruit. It is hard to stop once it takes hold: the fungus lives on in old leaves and crop trash, and every rain splashes fresh spores higher up the plant. That is why you must keep it off the top leaves from the start — by the time the whole plant is spotted, the harvest is already lost.
When to act
spots appearing on lower leaves and moving up the canopy, or defoliation beginning before the crop matures
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full leaf spot field guide
- Identify it
- Scout for it
- Control it
13 field-guide sections in the app
The full guide to leaf spot — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify leaf spot?
What you see first: small round to angular spots on the oldest, lowest leaves — the ones nearest the ground. They start pin-head size, are brown, tan or black, and many have a yellow ring (halo) around them like a target.
When should I take action against leaf spot?
spots appearing on lower leaves and moving up the canopy, or defoliation beginning before the crop matures
How do I control leaf spot?
Prevent it first — this is your strongest tool. Rotate: don't plant the same crop on the same land two seasons running — give it a 2-year break so the fungus in the old trash dies out. Clean up: after harvest, gather and burn or bury the infected leaves and crop trash so there are no spores to splash up next season, and always plant clean, healthy seed.
Which crops does leaf spot affect?
Among the crops covered here: Fonio, Ginger, Groundnut, Maize, Sesame, Tomato.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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